University officials say the atheist group has the right to conduct the swap.

UTSA spokesman David Gabler says, "As long as students are not violating laws or violating the Constitution, they have the freedom of speech and assembly."

The Atheist Agenda started at UTSA in 2005, and their first "Smut for Smut" campaign blew up into a national media sensation, reports CBS affiliate KENS in San Antonio. Past president Thomas Jackson was deluged with interview requests, and debated Tucker Carlson, the bow-tie-wearing conservative pundit, on MSNBC.

This year, organizers said a group of Christians amassed to protest the event, and one protester ripped a sign from someone's hands. But police kept a watchful gaze over students involved in heated debates, and did not report any violence.